(a) Field of the Invention
The invention relates to an umbrella structure, and more particularly, to an umbrella, which overcomes a drawback in a prior invention that is incapable of steadily stretching for use due to a reduced volume of the umbrella.
(b) Description of the Prior Art
Referring to FIGS. 1 and 1A, a prior umbrella 1 comprises a cover 11, a shaft 12, a notch 13, a runner 14, main ribs 15 and stretchers 16. Around the notch 13 is a plurality of pivotally disposed main ribs 15 for supporting the cover 11, whereas around the runner 14 is a plurality of pivotally disposed stretchers 16 for supporting the main ribs 15. The shaft 12 is in a two-sectional or multi-sectional form, and has a top end thereof fixed to the notch 13. The notch 13 is fastened with an inner tube 122, which has a rectangular fastening orifice 121 at an appropriate position for setting free a fastening button 17 disposed at the inner tube 122. The inner tube 122 is also penetrated through the runner 14, so as to allow the runner 14 with up-and-down sliding movements. When the umbrella 1 is stretched, the runner 14 is pushed upward to the fastening button 17 that further butts against a bottom portion of the runner 14, such that the main ribs 15 prop up the entire cover 11. The umbrella 1 is collapsed by pressing the fastening button 17.
As described above, although the prior umbrella 1 fulfills stretching and collapsing functions, a collapsed volume thereof is rather large when the shaft 12 is in two-sectional or multi-sectional form. The collapsed umbrella 1 is only suitable for carrying in larger handbags or backpacks but not in commonly used smaller-sized handbags. To reduce the volume of the umbrella 1, it is necessary to devise the shaft 12 as a multi-sectional design, with a difference between diameters of an outer tube and the inner tube of the shaft 12 being inevitably enlarged. When stretching the umbrella, a substantial space is left between the inner tube having the smallest diameter and the runner 14 having a diameter larger than that of the outer tube, so that undesired wavering and deviation of the runner 14 are produced when the shaft 12 performs up-and-down movements. Hence, the fastening orifice 17 at the shaft 12 becomes incapable of appropriately butting against the runner 14, with the runner 14 frequently sliding downward and failing to steadily stretching the umbrella.
Referring to FIGS. 2 and 2A showing another prior umbrella 2, a shaft 22 is devised as a four-sectional or five-sectional design for reducing the volume of the umbrella 2. As appropriate, one or two ends where stretchers 25 come into contact with a runner 23 are inserted and extended with extension posts 27. When stretching the umbrella 2, the shaft 22 is upheld by the extension posts 27 through the runner 23 to prevent the shaft 22 from producing undesired wavering. A fastening button 26 at the shaft 22 and a bottom portion 28 of the runner 23 allow a larger mutual supporting plane, thereby enabling the stretchers 25 connected with the runner 23 to prop up main ribs 24 that further stretch an entire cover 21. The umbrella 2 is collapsed by pressing the fastening button 26.
As described above, the prior umbrella 2 advances over the prior umbrella 1 by having a smaller volume. However, due to the extension posts 27 in the prior umbrella 2, the runner 23 requires slight turning to allow the fastening button 26 to avoid the extension posts 27 to stretch the umbrella for that the shaft is butted against by the extension posts 27; usage inconveniences of users are again caused.